Antennas have been applied on a large scale in reality along with increasing maturation of Active Antenna System (AAS) technologies. The quality of three-dimensional channels cannot be measured in the existing Long Term Evolution (LTE) and Long Term Evolution-Advanced (LTE-A) system, but after the antennas are applied on a large scale, the number of ports controllable by a base station can grow dramatically to 64 or even more, so that the three-dimensional channels can be increasingly applied. It is highly desirable to address the issue of how to measure effectively the quality of three-dimensional channels.
The quality of a channel is typically measured using a Cell-specific Reference Signal (CRS) and a Channel State Information-Reference Signal (CSI-RS) in the existing system, where the CRS is transmitted in each sub-frame, and at most four ports are supported; and a User Equipment (UE) can obtain the positions of resources occupied by the CRS according to a broadcast channel and a cell identifier (ID). The CSI-RS is configured periodically, and a transmission periodicity, the number of ports, and the positions of occupied resources are signaled in Radio Resource Control (RRC) signaling; at most eight ports can be supported; and the concept of a process is defined in the LTE-A system, where each process corresponds to one CSI-RS measurement resource, and each UE can be configured with a plurality of processes.
Controllable antenna elements are arranged in a two-dimensional pattern in the case of three-dimensional channels, but controllable antenna elements in the existing system are arranged in a linear array. Although multi-port channel measurement can be made by configuring a plurality of CSI-RS resources in the existing system, the CSI-RS resources are independent of each other, so that the UE cannot obtain the overall quality of the three-dimensional channels by jointing measurement results on the plurality of CSI-RS resources, and since the qualities of horizontal and vertical channels in the case of the three-dimensional channels are not totally independent of each other, it is highly desirable to address the issue of how to instruct the UE to obtain the overall information of the three-dimensional channels, and moreover a support of measuring the quality of the three-dimensional channels has been absent in the existing system.